1. Field of the Invention
The present invention relates to a receiving device and receiving method suitable for adaptively estimating a transmission path characteristic and equalizing a received signal in mobile communication, particularly orthogonal frequency division multiplex (OFDM) packet mobile communication, and a program for realizing these by a computer.
2. Description of the Related Art
In a packet radio communication system, there have conventionally been proposed various techniques for compensating for a distortion in a signal arriving through a plurality of transmission paths.
For example, there has been proposed a method wherein, for estimation of a transmission path characteristic, a sending device inserts a known signal into a preamble of a packet, and a receiving device estimates the first transmission path characteristic by comparing an actually received signal with the known signal (or its modulated signal). Further, the receiving device obtains a transmitted signal by equalizing a data signal coming after the known signal by using the first transmission path characteristic, and estimates the next transmission path characteristic by comparing the obtained transmitted signal (or its modulated signal, which is referred to as “replica”) with a corresponding portion of the actually received signal. The receiving device repeats this process for the following data signals.
Because a transmission path characteristic obtained in the above-described manner includes influences of noise, etc., there have been proposed such methods as described below for reducing the influences.
(1) To carry out averaging in a direction of a frequency axis.
(2) To carry out averaging in a direction of a time axis.
(3) To carry out averaging in a direction of a time axis, and abandon the obtained value if it is a prominent value.
In these techniques, equalization of a transmitted signal, generation of a replica, and estimation of a transmission path characteristic require time. That is, if the receiving process is performed in real time, an obtained transmission path characteristic is to be used for equalization of a received signal which arrives later by such a time as required for the equalization, the generation of a replica, etc. to be performed. Therefore, if the transmission path characteristic changes in this process performance time, there occurs a problem that the difference between the estimated transmission path characteristic and the actual transmission path characteristic is large, causing deterioration in the receiving characteristic.
The present invention was made for solving the above-described problem, an object of the present invention is to provide a receiving device and receiving method suitable for adaptively estimating a transmission path characteristic and equalizing a received signal in mobile communication, particularly OFDM packet mobile communication, and a program for realizing these by a computer.